A major cost problem experienced by the electronics industry is the loss of solderability of electronic components and printed circuit boards, particularly during storage. Poor solderability of component leads and printed wiring boards is believed to account for as much as 75% of solder joint failures. Because humid environments are known to exacerbate the problem, an electrochemical mechanism is clearly the cause of solderability degradation. In the lead-tin-copper solder system, for example, previous studies have determined that oxidation of the tin-lead (Sn-Pb) surface and underlying copper-tin (Cu-Sn) intermetallic layers is involved in the degradation process. In the past, however, the nature of the various oxides and their roles in the degradation of solderability remained obscure.
Traditional techniques typically employed in the prior art for surface analysis of circuit boards provide only subjective indicators of solderability. Currently used production test methods are also destructive by nature. Because degradation of solderability is known to involve an electrochemical mechanism, it is believed that solderability can be assessed more accurately and efficiently using electrochemical methods that provide in situ quantitative analysis of metallic oxides known to degrade solderability. In particular, there is a need for quantitative, nondestructive, electrochemical methods of solderability analysis that are easily applied for testing off-the-shelf components and for process control in the production environment.